Well I had an existing 'noise' with the aircon that when engaged and the engine was switched off there was a 'glug-glug-glug....' noise that sounded almost like a bottle emptying.

CPC identified the source just after I purchased the car as a bearing of some sort then - basically the wheel was still spinning (from inertia I guess) after the source of it's energy was removed.

Not sure if this is the compressor clutch or...?

This new noise happens only when the engine is running and the air con is engaged. Blowers inside the cabin sound a little more strained.

Assuming it's not a simple recharge of the gas how much do we reckon fixing aircon is nowadays? I appreciate it's not cheap. CPC's approach with the original element noted above was it's just noisy and not a problem to be fixed - very expensive to do so - so I'm assuming it's a 'how much!!!!!!!' sort of price tag